Manhattan Project


A few years after its invention in the early 1930s, John R. Dunning directed the development of a Columbia University cyclotron in the basement of Pupin Hall. Cyclotrons, also known as “atom smashers,” accelerate atoms through a vacuum to induce collisions at very high speeds—25,000 miles per second—via electromagnets. Among those working on the finished cyclotron was Herbert Anderson, a physics PH.D. student. In December 1938, German chemists Otto Hahn and Fritz Strassman detected barium by bombarding uranium with neutrons, subsequently making the discovery of nuclear fission. Niels Bohr1 hears about the news and travels to New York to find Columbia physicist Enrico Fermi; he doesn’t find Fermi in his office so he enters the basement of Pupin Hall and excitedly explains to Herbert Anderson the discovery2. Shortly after in January 1939, the Columbia experimental team—consisting of John R. Dunning, Enrico Fermi, Herbert L. Anderson, Eugene T. Booth, G. Norris Glasoe, and Francis G. Slack—conducts the first nuclear fission experiment in the US as they demonstrate the large energy release in the fission of uranium using Pupin Hall’s very own cyclotron. A year later, Columbia physicists identified the exact fissionable material in uranium—the rare isotope uranium-235—and concluded that it must be separated from the more prevalent uranium-238 isotopes and concentrated for use in a nuclear weapon. Dunning and Harold Urey headed a Columbia team in the invention and perfection of the “gaseous diffusion” method of separating uranium isotopes, which served as the building block for the K-25 gaseous diffusion plant built during the Manhattan Project.

Check out a pdf copy of the National landmark filing for Pupin Hall and a pdf draft of the press release, written at the time of the landmark designation. Extensive documentation on the Pupin Physics Laboratories can also be accessed at the National Archives Catalog listing

1Willis Lamb, a distinguished faculty member from Columbia, claims he was the physicist who shared the news of the European fission experiment to Herbert Anderson, not Bohr.

2Anderson retells the story of meeting Bohr in an interview at the American Institute of Physics.

Pupin Hall Uranium Experiments

In 2017, Shigeaki Mori, one of the last survivors of the Hiroshima nuclear explosion, visited Abhay Pasupathy and the Columbia physics department in Room 118—where the famous experiment took place. Pasupathy said, “Mr. Mori said to me that he now felt at peace with science and was happy to see me there in the lab and see how far the world had come."

Dunning Cyclotron

The Dunning Cyclotron was a component of an early particle accelerator hosted in the basement of the Pupin Physics Laboratories. Further reading can be found on the National Museum of American History, along with more pictures.